Silicon-carbonaceous encapsulated materials

ABSTRACT

A process includes preparing a solution including a silicon precursor or mixture of silicon precursors and a monomer or mixture of monomers; polymerizing the monomer to form a polymer-silicon precursor matrix; and pyrolyzing the polymer-silicon precursor matrix to form an electrochemically active carbon-coated silicon material.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional application of a U.S. patentapplication Ser. No. 13/217,691, filed on Aug. 25, 2011, incorporatedherein by reference in its entirety.

GOVERNMENT RIGHTS

The United States Government has rights in this invention pursuant toContract No. DE-AC02-06CH11357 between the United States Government andUChicago Argonne, LLC, representing Argonne National Laboratory.

FIELD

Generally, the present invention relates to materials for lithium-ionbattery electrodes.

BACKGROUND

Rechargeable lithium-ion batteries are now one of the primary powersources for consumer electronics. Such batteries were first produced inhigh volume by SONY and NEC Moli in the early 1990's. Since then, Li-ionbattery technology has been very successful at penetrating high-endconsumer electronic markets to replace lead-acid, Ni-Cd and Ni-MHrechargeable batteries. The worldwide annual production of Li-ionrechargeable batteries exceeds 2 billion cells, the majority of whichare small size cylindrical and prismatic cells whose capacities are lessthan 2.8 Ah (ampere hours). Due to their high energy density and longcycle-life compared to other battery technologies, Li-ion batteries arealso an attractive technology for larger size, high capacity and highpower rechargeable battery markets within the transportation,telecommunication and military applications. Furthermore, economical andenvironmental constraints have made these batteries the main focus forhybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV),and electric vehicles (EV).

A typical lithium-ion battery consists of a lithium-based transitionmetal (Mn, Co, Ni) material as the positive electrode, a carbonaceousmaterial (graphite or coke) as the negative electrode, and a non-aqueouselectrolyte. The battery also typically has a separator between thepositive and negative electrodes, and is typically enclosed in a case.Graphite/LiCoO₂, graphite/LiMn₂O₄, and graphite/LiFePO₄ and derivativesof these cell chemistries are the electrochemical energy storage systemsof commercial production interest. The electrolyte is typically asolution including a lithium salt, e.g. LiPF₆, dissolved in an organiccarbonate solvent. After two decades of extensive R&D, this technologyappears to have reached a maturity with regard to power and energydensity, despite several unsolved weaknesses.

One such weakness is related to energy density. A typical lithium-ionbattery can store about 150 watt-hours of electricity per kilogram. Forcomparison, six kilograms of lead acid battery are required to store thesame amount energy. This is a big stride indeed, but there is unlikelyto be further improvements in energy density with current materials anddesigns. Another weakness is with respect to safety. At full charge,carbonaceous anodes are highly reactive because they operate at apotential close to that of metallic lithium, where a film forms. Suchfilms, also known as the solid electrolyte interface (SEI), can be asource of thermal runaway when the electrode is subjected to external orinternal heat.

Metallic lithium anodes are not suitable in lithium batteries becausethey do not form a stable passivation film with conventionalelectrolytes. Graphite materials are widely used as anode materials incommercial cells, however, the life expectancy of the cells is largelyshortened due to irreversibility issues associated with the graphiticunstable solid electrolyte interface. It is also well known that lithiumforms alloys with several metals among which silicon and tin. In thiscase compounds such as Li_(4.4)Si and Li_(4.4)Sn can providesignificantly higher capacities. However, using such alloys as anodeswith lithium insertion cathode materials leads to volume expansion ofthe electrodes, which, in turn, leads to cell failure.

SUMMARY

To address the above concerns, silicon suboxide (SiO_(x)), siliconoxycarbide (SiO_(x)C), and silicon/carbon-encapsulated materials (Si/C)as hybrid structured materials for use as advanced anode materials forlithium batteries. Such materials may address dimensional instabilityissues typically associated with alloy cells. The carbonaceous matrixserves as the support for the metal or metal oxides of the alloys andprovide the dimensional stability during the lithium alloying process.The carbonaceous matrix can also establish the electronic conductingpathway within the electrode.

In one aspect, a process is provided including preparing a solution thatincludes a silicon precursor or mixture of silicon precursors, and amonomer or mixture of monomers; polymerizing the monomer or mixture ofmonomers to form a polymer-silicon precursor matrix; and pyrolyzing thepolymer-silicon precursor matrix to form an electrochemically activecarbon-coated silicon material.

In another aspect, a process is provided including contacting a siliconcompound with a carbon source gas at a temperature sufficient to degradethe carbon source gas to carbon and deposit the carbon on the surface ofthe SiO₂ to form SiO₂C or SiO_(x)C, wherein x is less than 2; whereinthe silicon compound is silicon, a silicon suboxide, a siliconoxycarbide, or a mixture of any two or more such materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C are x-ray diffraction patterns of pristine SiO₂(1A), carbon-coated SiO_(x)C prepared at 800° C. for 3 hours (1B), andcarbon-coated SiO_(x)C prepared at 900° C. for 3 hours (1C), accordingto Example 1.

FIGS. 2A and 2B are SEM images of SiO_(x)C, prepared at 900° C. for 3hours, according to Example 1, at lower (2A) and higher (2B)magnification.

FIG. 3 is a nitrogen isotherm of SiO_(x)C prepared at 900° C. for 3hours, according to Example 1.

FIG. 4 is a nitrogen isotherm of SiO_(x)C prepared at 700° C. for 3hours, according to the examples.

FIG. 5 is a thermal gravimetric analysis (TGA) graph of SiO_(x)Cmaterials coated at 800° C., 900° C., and 1000° C., according to theexamples.

FIG. 6 is a cyclic voltammograms for amorphous SiO₂ in a lithium cell,according to Example 1.

FIG. 7 is a voltage profile for a Li/SiO_(x)C cell, according to Example1.

FIG. 8 is a graph of specific capacity versus cycling of a Li/SiO_(x)Ccell, according to Example 1.

FIG. 9 is an SEM image of Si/C material according to Example 2.

FIG. 10 is a nitrogen isotherm graph of Si-C prepared at 700° C.,according to Example 2.

FIG. 11 is an energy dispersive x-ray of Si-C prepared at 700° C.,according to Example 2.

FIG. 12 is a voltage profile of a Li/SiO_(x)C cell, according to Example2.

FIG. 13 is a cyclic voltammogram for a Li/SiO_(x)C cell, according toExample 2.

FIG. 14 is a graph of specific capacity versus cycling of a Li/SiOxCcell, where the SiO_(x)C was prepared according to Example 1, at 900° C.

FIG. 15 is a graph of voltage versus specific capacity of a Li/SiO_(x)Ccell, where the SiO_(x)C was prepared according to Example 2.

DETAILED DESCRIPTION

In one aspect, a process is provided for preparing an anode materialthat includes solution phase reactions. The process includes, but maynot be limited to, preparing a solution of a silicon precursor and amonomer or mixture of monomers, polymerizing the monomer or mixture ofmonomers to form a polymeric-silicon precursor matrix, isolating thepolymeric-silicon precursor matrix, and pyrolyzing the polymeric-siliconprecursor matrix to form an electrochemically active, carbon-coatedsilicon material. Illustrative active materials include SiO₂C orSiO_(x)C, where x is less than 2.

In the process, the monomers and the silicon precursor are intimatelymixed to form the solution. The solution may include the monomers as aneat, liquid mixture, or the solution may also include a solvent. Forexample, illustrative solvents include acetic acid, adipic acid, citricacid, oxalic acid, lactic acid, ascorbic acid, and folic acid. Mixturesof such solvent (acid solvents) may be used. The solution may then beheated to polymerize the monomers.

Suitable silicon precursors include those which are soluble in eitherthe solvent, or the monomers. In some embodiments, the siliconprecursors are soluble in the solvent. For example, the siliconprecursor may be soluble in acetic acid. In such cases, upon contact ofthe silicon precursor with the monomer solution a colloidal suspensionis formed. Upon heating, the monomers polymerize trapping the colloidalsuspension within a polymer matrix. After polymerization, the solvent isevaporated to leave a silicon material-powder composite. During theheating and polymerization, the silicon precursor is converted to asilicon material that may include oxides of silicon, silicon alkoxides,or other silicon-containing species. The silicon material-powdercomposite is then pyrolyzed.

As noted, the silicon precursor is a soluble silicon containingmaterial. Illustrative materials include, but are not limited to,silicon acetate, silicon ethoxide, silicon propoxide, or siliconisopropoxide.

Suitable monomers include those that will polymerize leading to theformation of a polymeric matrix around the silicon precursor material.The polymeric matrix that is formed includes gel particles of polymer.Upon pyrolysis, the gel particles are converted into carbonmicrospheres. Suitable monomers may include, but are not limited to,phenol, urea, benzene-1,3-diol, benzene-1,2-diol, benzene-1,4-diol,methylene phenyl diisocyanates, styrene, methyl methacrylate, vinylchloride, vinyl fluoride, toluene diisocyante, melamine, formaldehyde,and other functional monomers. Mixtures of the monomers may also beused. In one embodiment, the monomers are a mixture of formaldehyde andbenzene-1,2-diol. In another embodiment, the monomers are a mixture offormaldehyde and benzene-1,3-diol. In yet another embodiment, themonomers are a mixture of formaldehyde and benzene-1,4-diol. In yetanother embodiment, the monomers are a mixture of formaldehyde andphenol. In yet another embodiment, the monomers are a mixture offormaldehyde and urea. In yet another embodiment, the monomers are amixture of formaldehyde and methylene diphenyl diisocyante. In yetanother embodiment, the monomers are a mixture of formaldehyde andtoluene diisocyante. In yet another embodiment, the monomers are amixture of formaldehyde and melamine.

The heating of the monomer and silicon colloidal suspension is to beperformed at a temperature that is sufficient to polymerize the monomeror mixture of monomers. For example, the polymerization may be effectedby heating the monomers at a temperature greater than about 25 C. Insome embodiments, the temperature is greater than about 60 C. In otherembodiments, the temperature is greater than about 70 C. In some otherembodiments, the temperature is from about 25 C to about 150 C. In someother embodiments, the temperature is from about 70 C to about 150 C.The polymerization is conducted at temperature for a time periodsufficient to prepare the polymers. In some embodiments, the time periodis greater than 10 minutes. In other embodiments, the time period isgreater than 1 hour. In other embodiments, the time period is greaterthan 2 hours. In some other embodiments, the time period is from about10 minutes to about 5 hours. In yet other embodiments, the time periodis about 2 hours.

The polymerization may also be a free-radical polymerization. Forexample, an initiator such as a peroxide, an azo compound, a persulfate,or other initiator as known in the art may be used. The polymerizationsmay also be initiated photolytically, by exposing the monomer mixture toUV light.

The pyrolysis is then performed to convert the carbon material that isthe polymer to a carbon deposit (i.e. carbon microspheres as describedabove), which forms on the silicon as it is being converted from thesilicon-containing material. The temperature of the pyrolysis is suchthat the silicon material-powder composite degrades to theelectrochemically active, carbon-coated silicon material. In someembodiments, the temperature is from about 400° C. to about 1600° C. Inother embodiments, the temperature is from about 700° C. to about 1200°C.

According to some embodiments, the pyrolyzing is conducted under areducing atmosphere. Such a reducing atmosphere may include a gaseousmixture including, but not limited to, hydrogen, carbon dioxide, carbonmonoxide, acetylene, butane, 1-3 butadiene, 1-butene, cis-2-butene,trans-2-butene, 2-2 dimethylpropane, ethane, ethylene, isobutane,isobutylene, methane, propane, toluene, and propylene. Mixtures of anytwo or more such gases may also be used. In some embodiments thereducing gas is provided with an inert gas. Suitable inert gasesinclude, but are no limited to, nitrogen, helium, and argon. Mixtures ofany two or more inert gases may be used. The ratio of reducing gas toinert gas may range from about 5:1 to about 1:5. In some embodiments,the ratio of reducing gas to inert gas may be about 1:1.

The process may be conducted in a furnace with a reaction having theappropriate connections effect filling of the chamber with a carbonsource gas, and, optionally, evacuation of the chamber. Thus, blastfurnaces, rotary furnaces, fluidized bed furnaces, tube furnaces, orother similar equipment may be used, in some embodiments.

In another aspect, a process is provided for preparing an anode materialthat includes gas phase deposition. The process includes, but may not belimited to, depositing a carbon layer on a silicon-containing materialvia carbon deposition from a carbon source gas in the presence of thesilicon-containing material. The silicon compound is silicon, a siliconsuboxide, a silicon oxycarbide, or a mixture of any two or more suchmaterials. According to various embodiments, a silicon-containingmaterial is a exposed to a gas that includes a carbon source at atemperature sufficient to degrade the carbon source gas to carbon, whichthen deposits on the silicon-containing material to form SiO₂C orSiO_(x)C, where x is less than 2 and greater than or equal to 0. Thetemperature is greater than 500° C. According to various embodiments,the temperature is greater than 600° C., greater than 700° C., greaterthan 800° C., or greater than 900° C. In some embodiments, thetemperature is from 500° C. to about 1000° C. In other embodiments, thetemperature is about 700° C., about 800° C., about 900° C., or about1000° C.

The silicon-containing material may be a silicon particle, a silicondioxide (SiO₂) particle, or a silicon suboxide (SiO_(x)) particle, where0≦x≦2. In some embodiments, the silicon-containing material is SiO₂. Thesilicon-containing material may be crystalline in some embodiments, oramorphous in other embodiments. In some embodiments where thesilicon-containing material is SiO₂, it is pristine, amorphous SiO₂. Asused herein, pristine means having a purity of 99% or greater. Forexample, in some cases, the purity of pristine SiO₂ is 99.9% or greater.In other embodiments where the silicon-containing material is SiO₂, itis produced by the Stöber method. The Stöber method is defined as amethod where an alcohol, saturated alcoholic ammonia solution, ammoniumhydroxide, and water are mixed. To the mixture is added an alkylsilicate, the resulting mixture being agitated to form a turbid whitesuspension. The suspension is then recovered by filtration. A moredetailed description of the method may be found in Stöber et al. J.Colloid Interface Sci. 26:62 (1968), which is incorporated herein byreference.

The carbon source gas may be any hydrocarbon that will degrade to carbonat the temperature. For example, the carbon source gas may be any C₁-C₁₂alkane, C₁-C₁₂ alkene, or C₁-C₁₂ alkyne. In some embodiments, the carbonsource gas is methane, ethane, n-propane, n-butane, 2-methylpropane,n-pentane, 2-methylbutane, 2,2-dimethylpropane, hexane, ethylene,propylene, 1-butene, cis-2-butene, trans-2-butene, 2-methylpropene,1,3-butadiene, 1-pentene, 2-pentene, 3-pentene, 2-methyl-l-butene,2-methyl-2-butene, 3-methyl-1-butene, hexene, acetylene, acetylene,1-butyne, 2-butyne, 1-pentyne, 2-pentyne, 3-methyl-1-pentyne, hexyne, ortoluene. In some embodiments, the carbon source gas is ethylene orpropylene.

In one aspect, an anode material is provided including a carbonaceousmatrix that at least partially surrounds a material including silicon, asilicon suboxide, a silicon oxycarbide, or a mixture of any two or moresuch materials. Such materials are those as described above which areprepared by either the gas phase methods or solution phase methods. Suchmaterials are electrochemically active in lithium cells. In oneembodiment, the carbonaceous matrix encapsulates the silicon, siliconsuboxide, silicon oxycarbide, or a mixture of any two or more suchmaterials.

The anode materials may be fabricated into an anode by combining theanode materials described above with a binder, and contacting themixture with a current collector. The current collector serves theelectrical connection from the anode material to a circuit. The mixtureof the anode material and the binder is typically prepared by millingthe anode material with the binder in a solvent to form a paste. Thepaste may then be applied to the current collector and dried to form theanode. Suitable binders include, but are not limited to, polymericmaterials such as polyvinylidenedifluoride (PVDF), carboxymethylcellulose, polyimide, styrene-butadiene rubber,poly(acrylamide-co-diallyldimethylammonium chloride), and polyacrylicacid. Combinations of any two or more such polymeric materials may beused. The solvent this used to form the paste may be any that iscompatible with the anode material and the binder, and will notadversely affect an electrochemical cell if residual solvent remains.Illustrative solvents include, but are not limited to,N-methylpyrrolidone (NMP), ethanol, acetone, and methanol. Combinationsof any two or more such solvents may be used.

In another aspect, an electrochemical device is provided including ananode as described above and which includes a carbonaceous matrix thatat least partially surrounds a material including silicon, a siliconsuboxide, a silicon oxycarbide, or a mixture of any two or more suchmaterials. The electrochemical device may also include a cathode and anon-aqueous electrolyte.

Suitable cathode materials include, but are not limited to, LiCoO₂,LiFePO₄, LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, LiMn₂O₄, andLiNi_(0.5)Mn_(1.5)O₄. The cathode may include a mixture of any two ormore such materials.

Suitable non-aqueous electrolytes include a solvent and a salt. Suitablesolvents for the non-aqueous electrolyte include, but are not limitedto, carbonate-based solvents, oligo(ethyleneglycol)-based solvents,fluorinated oligomers, dimethoxyethane, triglyme, dimethylvinylenecarbonate, tetraethyleneglycol, dimethyl ether, polyethylene glycols,sulfones, sulfolane, and γ-butyrolactone. Of course, the solvent may bea mixtures of such solvents. The solvents support lithium-ion and oxygentransport through electrochemical cells prepared with the solvents.

In some embodiments, the salt is a lithium salt. Illustrative lithiumsalts are not particularly limited, as long as it dissolves in thesolvent of the electrolyte. Illustrative lithium salts that may be usedin the electrolytes include, but are not limited to, LiClO₄, LiBF₄,LiAsF₆, LiSbF₆, LiPF₆, LiCF₃SO₃, Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, LiC₆F₅SO₃,LiAlCl₄, LiGaCl₄, LiSCN, LiO₂, LiCO₂CF₃, LiN(SO₂C₂F₅)₂, lithium alkylfluorophosphates, lithium bis(oxalato) borates Li[B(C₂O₄)₂] andLi[BF₂C₂O₄], Li₂B₁₂X_(12-n)H_(n), wherein X is OH, F, Cl, or Br, and nranges from 0 to 12, or Li₂B₁₀X_(10-n)H_(n), wherein X is OH, F, Cl, orBr, and n ranges from 0 to 10.

The present technology, thus generally described, will be understoodmore readily by reference to the following examples, which are providedby way of illustration and are not intended to be limiting.

EXAMPLES

General. Pristine, amorphous SiO₂ was prepared using tetraethylsiloxane(TEOS), ethanol, and distilled water according to the Stöber method. TheSiO₂ obtained by the method is amorphous.

Example 1

General Gaseous Coating Method. The carbon-coating process was carriedout in a preheated furnace reactor (at 700° C., 800° C., 900° C., or1000° C.). In the reactor, a propylene-nitrogen mixture as the carbonsource was fed to SiO₂ prepared by the Stöber method (above). The carboncoating experiments were carried out at furnace temperature for 3 hours.No crystallization of the amorphous SiO₂ was observed by the completionof these experiments. The SiO_(x)C materials obtained are black incolor, thereby indicating carbon uptake.

Typical coating method. SiO₂ (3 g) is introduced in a rotary furnace andthen heated up to 700° C., 800° C., 900° C., or 1000° C. The furnace isflashed with a gas that includes propylene and nitrogen in a ratios of1:9, and the furnace is held at temperature for 3 hours. The furnace isthen cooled to room temperature, and the carbon coated SiO₂ collected.

Characterization. FIG. 1 includes the x-ray diffraction (XRD) patternsof pristine SiO₂, and carbon-coated SiO₂ (SiO_(x)C) at 800° C. and 900°C. for 3 hours. The XRD patterns show that the material remainsamorphous and no other phase, such as SiC, has formed during the heattreatment.

FIGS. 2A and B show the scanning electron microscopy images of SiO_(x)-Ccoated at 900° C. Clear evidence of the carbon shell can be noticedsurrounding the spherical SiO_(x) particles. FIG. 3 shows the nitrogenisotherm of SiO_(x)-C coated at 900° C. for 3 hours. FIG. 4 shows thenitrogen isotherm of SiO_(x)-C coated at 700° C. for 3 hours. Thesurface area values were 7.6 and 15.2 m²/g for the materials coated at900° C. and 700° C., respectively. The decrease in surface area whileincreasing the temperature indicates that a larger content of carbon hasbeen deposited on the surface of SiO_(x) particles.

FIG. 5 shows the thermal gravimetric analysis of SiO_(x)C materialscoated at 800° C., 900° C., and 1000° C. The materials were coated for 3hours. The carbon uptake for the material that was coated at 900° C. was33% per weight. In other words, the particles contains 33 wt % carbon.The curves shows the amount of carbon uptake and the temperature abovewhich the carbon was removed. For each of the samples, the temperatureat which the carbon was removed was about 600° C.

FIG. 6 shows the cycling of amorphous SiO₂ in a lithium cell. Electrodeswere prepared using of 80 wt % active material, 10 wt % acetylene blackas the conductive agent, and 10 wt% polyvinylidene difluoride as thebinder. Electrodes having a surface area of 1.6 cm² were assembled intoCR2032-type coin cells within a helium atmosphere in a glove box.Lithium was used as the negative electrode. Copper was used as thecurrent collector. A solution of LiPF₆ (1.2M in ethylene carbonate:ethylmethyl carbonate 3:7 by volume) was used as the electrolyte. The Li/SiO₂cells exhibited a 20 mAh/g specific capacity. For reference, a typicalgraphite anode delivers a specific capacity of about 300 mAh/g.Accordingly, by comparison, SiO₂ is an almost inactive anode material.However, the SiO_(x)C greatly improves the anode capacity. FIG. 7 showsthe voltage profile of a Li/SiO_(x)C cell, which exhibits an improvementof the capacity upon cycling with an average voltage of about 0.25V.

FIG. 8 is a graph of the specific capacity versus cycling of aLi/SiO_(x)C cell. The capacity of the cell improved with cyclingstarting from around 300 mAh/g to above 400 mAh/g.

Example 2

Solution Coating Method. To prepare a silicon-carbon encapsulatedmaterial, silicon acetate was dissolved in acetic acid with stirring.After the formation of a colloidal suspension, a formaldehyde solutionof benzene-1,3-diol was added. Heating of the solution led to thepolymerization of benzene-1,3-diol and formaldehyde. The acetic acid wasthen evaporated. The dry powder (about 5 g) was pyrolyzed under areducing atmosphere of H₂/He (3:97) at 700° C. for 4h.

Characterization. FIG. 9 shows the scanning electron microscopy image ofthe Si/C encapsulated material illustrating spherical carbon embeddingsilicon and silicon oxide. FIG. 10 shows the nitrogen isotherm of Si-Cprepared at 700° C. The surface area of the material reached 330 m²/g.FIG. 11 shows the energy dispersive x-ray of Si-C prepared at 700° C.The main elements that were present within the matrix of the hybridmaterial are carbon and silicon with existence of amounts of oxygenbonded to silicon.

FIG. 12 shows the voltage profile of Li/SiO_(x)C cell fabricated withthe material prepared at 700° C. from Example 2. The initial dischargecapacity of the cell was 700 mAh/g. The reversible capacity remainedaround 300 mAh/g. FIG. 13 shows the cycling of Li/SiO_(x)C cell. Thecell capacity remained constant for 100 cycles.

The two methods (gaseous coating and solution coating) provide a way toprepare SiOxC composites which show excellent electrochemicalperformance when used as anodes for lithium ion batteries. The gas-phasereaction enables the preparation of SiOxC particles with a carbonaceousnetwork that activates the electrochemical properties versus lithium.The pristine material has been shown to be electrochemically inactive.The solution phase process provides an efficient method allowing for thedirect integration of the carbonaceous network through polymerizationwith the SiO_(x) thereby forming a composite that is active as an anodefor lithium ion batteries. The above described methods enable the energyand power of SiOx-C anodes without jeopardizing the safetycharacteristics.

For the purposes of this disclosure and unless otherwise specified, “a”or “an” means “one or more.”

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “about” will mean up to plus or minus 10% of the particular term.

All publications, patent applications, issued patents, and otherdocuments referred to in this specification are herein incorporated byreference as if each individual publication, patent application, issuedpatent, or other document was specifically and individually indicated tobe incorporated by reference in its entirety. Definitions that arecontained in text incorporated by reference are excluded to the extentthat they contradict definitions in this disclosure.

The embodiments, illustratively described herein may suitably bepracticed in the absence of any element or elements, limitation orlimitations, not specifically disclosed herein. Thus, for example, theterms ‘comprising,’ ‘including,’ ‘containing,’ etc. shall be readexpansively and without limitation. Additionally, the terms andexpressions employed herein have been used as terms of description andnot of limitation, and there is no intention in the use of such termsand expressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the claimed technology.Additionally, the phrase ‘consisting essentially of’ will be understoodto include those elements specifically recited and those additionalelements that do not materially affect the basic and novelcharacteristics of the claimed technology. The phrase ‘consisting of’excludes any element not specified.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent compositions,apparatuses, and methods within the scope of the disclosure, in additionto those enumerated herein, will be apparent to those skilled in the artfrom the foregoing descriptions. Such modifications and variations areintended to fall within the scope of the appended claims. The presentdisclosure is to be limited only by the terms of the appended claims,along with the full scope of equivalents to which such claims areentitled. It is to be understood that this disclosure is not limited toparticular methods, reagents, compounds compositions or biologicalsystems, which can, of course, vary. It is also to be understood thatthe terminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as ‘up to,’ ‘at least,’ ‘greater than,’ ‘less than,’ and the like,include the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

While certain embodiments have been illustrated and described, it shouldbe understood that changes and modifications can be made therein inaccordance with ordinary skill in the art without departing from thetechnology in its broader aspects as defined in the following claims.

What is claimed is:
 1. A process comprising: contacting a siliconcompound with a carbon source gas at a temperature sufficient to degradethe carbon source gas to carbon and deposit the carbon on the surface ofthe silicon compound to form SiO₂C or SiO_(x)C, wherein x is less than 2and greater than zero; wherein: the silicon compound is silicon, asilicon suboxide, a silicon oxycarbide, or a mixture of any two or moresuch materials.
 2. The process of claim 1, wherein the silicon compoundis SiO₂ produced by the Stöber method.
 3. The process of claim 1,wherein the temperature is from about 400° C. to about 1600° C.
 4. Theprocess of claim 1, wherein the carbon source gas comprises a C₁-C₁₂alkane, a C₁-C₁₂ alkene, a C₁-C₁₂ alkyne, or a mixture of any two ormore such gases.
 5. The process of claim 1, wherein the carbon sourcegas comprises methane, ethane, n-propane, n-butane, 2-methylpropane,n-pentane, 2-methylbutane, 2,2-dimethylpropane, hexane, ethylene,propylene, 1-butene, cis-2-butene, trans-2-butene, 2-methylpropene,1,3-butadiene, 1-pentene, 2-pentene, 3-pentene, 2-methyl-l-butene,2-methyl-2-butene, 3-methyl-l-butene, hexene, acetylene, acetylene,1-butyne, 2-butyne, 1-pentyne, 2-pentyne, 3-methyl-1-pentyne, hexyne, ortoluene.
 6. An anode material comprising the electrochemically activecarbon-coated silicon material produced according to claim
 1. 7. Ananode material comprising the SiO₂C or SiO_(x)C produced according toclaim
 1. 8. An electrochemical device comprising the anode material ofclaim
 6. 9. An electrochemical device comprising the anode material ofclaim 7.